5th wheel weight problem:no traction

[OneWelder]

I am wondering about the "Bridge law" - I am sure rig or frank could explain this better than I but you may find the trailer is rated for the weight , but not legal to carry its rated load- I know there is a grandfather clause for some short trailers , but i do not know if manufacture date enters into it or if it is just certain lengths of trail.
also if I read you correctly you have a gross trl./tank weight of 47000 with most being on trailer- I do not think the spacing is right for you to get 20000 on those axles
Most trailers of that type are just made of common structural steel.
My advice would be to take to a Trailer shop ( there is usually a company around that builds trailer dumps ,lowbeds, trk bodies etc. ) Ask them about lengthen it = if you had all stripped and ready and just hired them to do trailer frame it would probably not be a lot of money

 

[Dirtmaster]

I did check with a local place, and their quote made me spit out my coffee. Near fell offa my horse, too. What I really need is some info on the proper weight distribution and what the effect of improper weight distribution is.
One issue is a panic stop. The tractor tandem duals will act as the front tires in a sudden stop. Weight will shift up there. Weight will lighten off of the trailer duals. How much is the question. I can calculate the increased loading by assuming a G-force deceleration. I can also stuff some dunnage up front and climb up a bit over the gooseneck, but I'm concerned about the vertical height of the center of gravity. The deck is 43 inches up already. The CG is likely about 30 inches off the ground in the front. The rear would be higher, but the dunnage won't lift the rear end. From the pictures of that track hoe tilted up on dunnage, my load is trivial. Even still, not looking forward to spots in my shorts on corners.
The wheel loading for bridge calculations is irrelevant, due to a grandfather clause. I can prove that the trailer was in service in this state prior to enactment of the bridge regulation. No problem, there.
Anyone know of a source of trailer design equations? Surely the manufacturers are going by some sort of book that speaks to load distribution for handling safety. There are rules for axle loading, but I'm more concerned with dynamic handling. Not trying to hot rod the rig. Just trying to make sure I end up with a rig that doesn't fishtail in a panic stop and also that I have sufficient weight to not lose traction on dirt hills.
Thanks!

 

[Safety Mgmt.]

I think your making a lot more out of this traction problem than needed. Think about doing this; Go to a metal salvage yard get them to loan you a big steel or wood box, have them fill the box with cut up railroad rail material or similar heavy iron, go over their scales and bring the weight up on your tractor drive tires to just under maximum weight listed on the tires of the tractor. Chain down the box good and go for a drive up hills, around corners, dirt hills and find a safe place to do a hard brake stop. (Make sure you've chained to box on good). If your performance and traction greatly improve with this weight on the fifth wheel area, then go back to the metal salvage yard and have them help find a casting or something as a single load you can chain down and maybe weld also to the plate above the fifth wheel area. You will be adding offsetting weight to the traction area only. You'll not have to drive the unit any higher up onto the front yoke or fifth wheel area and get into bridge height problems. You just need traction and we all pretty much agree that it will take weight over the rear tractor tires. Remember if you do this cure do-not exceed the tires weight listed on the rubber. Two tires will give you 2x the weight Example: One tire at 80 lbs will handle 3200# times two drive tires = 6400# total on both tires. Take the carrier loaded to the metal salvage yard to weight on the scales before you start loading the box up with weight.

 

[Dirtmaster]

I appreciate the thought, but there are a couple of problems with doing that. One; I haul it with an old Screaming Jimmy with only 318 hp and it's already slow. Two; if I add weight anywhere on this trailer, it affects the ability to tilt it do load it. The bed pivots between the tires, plus a second pivot in front of the front tires about a couple of feet. As it tilts down in back, the gooseneck also tilts down in front. Any weight I add will need to be exactly balanced fore and aft of the kingpin, which is possible to do of course.
I think adding weight will surely cure the traction problem, but to add enough weight to put half the towed weight onto the 5th wheel would necessitate a huge weight. Trailer and tank are already right about 50,000 pounds with virtually no weight on the 5th wheel.
By lengthening ($$$) the underframe 10 feet, I calculated that I'd be raising the 5th wheel weight to about 13000 to 15000 pounds, which is still nowhere near 50% of the towed weight.

 

[Safety Mgmt.]

I think your way off on the tongue weight having to be 50% of the 50,000#. My 7,500# trailer only has 800# tongue weight which is plenty. You cannot exceed what is on the rubber on the tires of the tractor. So again if the tires say 3,200 lbs at 65 lbs. of air pressure then you can only put 3,200# X 4 tires = 12,800 lbs. on those four rear tires. Remember that exceeding this weight is more unsafe than any other thing, a blowout when going down the road could kill you and others out there. Get back to me on what the weight at max air is on the side of the tires of the tractor. Also if your going to add ten feet to the trailer, it would be time consuming, quite expensive, and cheaper to find another used trailer and sell this one. The unit can go up ramps instead of having a tilt trailer!

 

[AtlasRob]

I think your way off on the tongue weight having to be 50%

I agree, 50% is way too much, which is one reason I bet a pint of beer a few posts back that a 4' extension on that trailer would be more than enough to get the weight on the pin that you need.


Have you tried to do the pivot test that rigandig suggested.

on edit, you might have miss read Safety Mgmt post as he is talking about adding weight to the puller NOT the pulled. You then reply about the problems with the tilting of the trailer.

 

[CinOK]

Have you ever tried scaling it loaded and then flipping it and rescaling.Those short trailers are pain to balance. How much does that thing weigh. I think the suggestion about ramping it up iis goint help, can you reposition the fifth wheel and still have the swing you need. I always had sliders on my tractors and ones that I drove.

 

[CinOK]

I cant tell by looking but somehow i think that thind is tail haeavy with the turret and armor it.

 

[Dirtmaster]

Hiya guys,
I have not had a chance to weigh it, but I do have a portable scale. The trailer is not here right now, anyway. The figure of 50% load on the front end is one that various seasoned truckers have given me. I'm looking for an authoritative book where such weight distribution is discussed formally. My tractor is a Freightliner cabover and is rated for 80,000 pounds. The load vehicle weighs 39000 pounds, the trailer weighs 12000. Tractor is about 16000. Tires are 11.00-24.5 and run at 100psi. In a sudden braked stop, I want to make sure the whole shebang stays straight. If the bulk of the weight is on the wheels directly under the load, I'm depending on the fairly light truck to stay straight. Without much gooseneck weight, I have very little traction. I just don't know what I really need up there for weight, and I'm very reluctant to just try something.Too dangerous to be guessing.

 

[amtronic]

Put a couple of 55 gal drums on the tongue, fill them with water. Instant ballast, you can dump it anywhere. Just secure the drums!

 

[AtlasRob]

............. In a sudden braked stop, I want to make sure the whole shebang stays straight. ...........................................

If the bulk of the weight is on the wheels directly under the load, I'm depending on the fairly light truck to stay straight.

The way to make sure you stay straight is to ensure that your trailer brakes are performing above and beyond the call of duty. That way the maximum weight is stopping the best, and holding back the puller, not trying to be stopped by the puller which is when you get into major dramas.

Many many years ago a small country plant company I worked for (17yrs old ) used to move their IH
B100 drotts and IH BTD8 dozers on a twin axle trailer behind a Fordson powermajor 4 wheel drive tractor, that puller had no hope in hell of stopping or holding that load on a steady let alone steep grade never mind in an emergency stop using the tractors own brakes. It was rigged with an an air operated lever on the offside mudguard ( no cab or roll bar back then ) which worked the trailer brakes. The biggest fear if you had to stop in a hurry was having a bucket or blade hit you in the neck ..........Chains, doh! I knew there was something missing with those loads :Banghead

Oh! to be young, stupid and immoral, oops! meant immortal ( we all thought we were are at that age..........didn't we ) :drinkup

 

[Dirtmaster]

Trailer load dynamics

Here is what I've learned from several truckers with decades of staying alive behind the wheel. The combination of truck and trailer can be viewed as one vehicle, that being the heavy trailer. The rear wheels of that vehicle are comprised of the rear tandem duals. The front wheels of that vehicle are the tandem duals of the tractor. The only thing the tractor does is aim it straight and provide a pulling force. In fact, my old 1970 tractor has no front brakes at all and never had them from the factory. Weren't required back then, nor were they desired by everyone. So now we have a heavy vehicle with tandem duals on each end. In a sudden stop, the wheels apply a braking torque, which translates to a braking force at the tire/road interface. The center of gravity is up above the road by roughly 6 feet. As braking force is applied at the ground level, the center of gravity (CG) keeps going forward in an attempt to rotate about the wheel/road point. That rotation lifts weight off of the rear tires and applies it to the front tires. The forward/aft position of the CG is well aft of the front wheels, so the downward force of the CG is lessened by the long moment arm of the forward portion of the trailer. I need lots of downward force on the 5th wheel plate to insure that the front of the trailer does not slide sideways, which would be a jack-knife. Once the front tandem duals start to slide, the coefficient of friction is far less and only gets worse.
What I cannot find is any engineering data on load distribution for dynamic stability of a trailer. I may create a computer model of a simple trailer and load, and see if I can get it analyzed in SolidWorks. Failing that, I'll try to model a simplistic version, assuming a deceleration due to a rapid stop. Alternatively, I could roll down the window, spit out a load of 'chaw' , and say " hell, let's just try it!". Any mechanical engineers out there that can weigh in on this? Thanks.

 

[CinOK]

You are correct the explanation was a bit over my redneck enginering degree. But the main problem is load placement and trailer lenght. When I pulled flatbed it was 48' spread with a shaker century tractor. I could scale a 50,000 coil if it was placed right If i palced lighter coilers incorrectly I could still be legal on my axle weights but my ride sucked and in any wet road conditions I would be working the crap out of the trolley brake. The deisn flaw is the short trailer in your case. Do you have a trolley on yours. I am assuming that all the brakes are in top shape. You can engineer anything to death but you have had suggestions from flatbeders and wide high and heavy guys the methos may be a little differnt but the basic function is to put more weight on the 5th wheel.
They did not require front brakes on older tractors in order to avoid front wheel slides but most had tolley brakes and many an old timer's seat had to be recoverd after he sucked it up as he was yanking on that trolley to get the trailer straight.

 

[CinOK]

Just a thought but if you know the weights of everthing one of the guys might have a loading programing> I know the have programs for this some of our expert dispatcher used to use them to tell use how to load, not that we listened :bash

 

[bill onthehill]

Why don't you contact Chaz Murray? He posts on here and has a trailer manufacturing company in California. I am sure he can steer you in the right direction.

 

[td25c]

I like the tank Dirtmaster,There are a few jobs I'v done in the past that a tank would have came in handy.That is a short tilt deck Rodgers trailer.I would experiment with ramps on the trailer and park the tank up on the neck of the trailer closer to the fithwheel.Looking at the picture on your first post you only need 6 or 8 inches to clear the neck on the trailer from the belly of the tank.Moving the tank forward 4 or 5 feet will make a huge difference in the wieght on the truck as other members have said.Dont worry about it getting to high on the center of gravity.That tank sets pretty low to start with and it will just be the front of the tank on the neck of the lowboy.It's not any different then when we put the blade of a dozer up on the neak of the trailer and they pull fine.Good luck with it.

 

[Dirtmaster]

Thanks for the tips. I do have a portable truck scale I can use. It's like a briefcase. I've even gone to the trouble of calibrating it against a known good, certified truck scale. I do plan on weighing every wheel with and without the tank. From that, I can calculate the loading on each wheel as I vary the positioning of the tank. I assume I will be able to find a spot where it works, but the whole shebang is still going to be kinda short. So long as it's safe, shorter is better for me.
The front end is where the engine, steering gear, and tranny are located, so it's a little nose heavy. Not much, but some. You can feel it in turns.
A friend borrowed this trailer to haul a logging skidder and it worked fine. In that case, he had the blade up on the gooseneck. Seemed to make a perceptible difference.

 

[td25c]

Tell us more about the tank Dirtmaster

Thats pretty cool Dirtmaster.I keep calling it a tank but it looks like a smaller version of an M-109 howitzer.My dad ,"seen unchaining the 16-b dozer in the picture" , was a gunner on an M-109 mobile howizer in Vietnam.He is no stanger to heavy equipment.He tolled me the M-109 had the detroit diesel in the front & drove from the front sprockets like your tank.Also had rear ground spades that dug in like outriggers when firing and an allison auto tranny in it.Keep us posted Dirtmaster.

 

[Dirtmaster]

Very perceptive of you. The 'tank' is actually a self propelled howitzer, very much like the M109 your dad served on in Vietnam. Ours is British, and called an Abbot. It's a kissing cousin of the US M108, which was the little brother to the M109. The M108 was a 105mm, as is the Abbot. They fired broadside instead of straight forward because the concussion of the gun would blow out the headlights. Didn't do wonders for the driver, either. Well actually, the driver was never up in his spot while firing. He was helping feed ammo to the loader guy in back. Shooting specs are: 50 pound round, 10.5 mile range. The barrel on this one has been demilled or deactivated or just plain screwed up to federal specs. Look up British Abbot FV433 on Google to see full specs.
Wish I could find a removable gooseneck or a folding gooseneck trailer that I could afford. It gets a little scary crawling up a stepdeck with virtually no vision and narrow tracks. Construction vehicles have much wider tracks than this unit. I have to be dead on accurate to load onto a 102" trailer. If I miss even a little, I go over the side. Been there; done that. Prefer not to do that again

 

[td25c]

Thanks for the information Dirtmaster.Your Abbot howitzer would make an interesting thread just by itself.Cool!